At present, CNC high finish machining process (milling, turning) is not well known by technicians in most industrial industries. The actual work shows that they are really controlled by only a few production enterprises. The main reason is that the demand is not very strong in the past, which is also closely related to cognitionIn recent years, with the development of high-performance and high-precision CNC machine tools and the emergence of high-performance metal cutting tools, CNC high finish machining has made a great breakthrough. It is possible to replace grinding with milling (turning), which has become the goal pursued by the machining industry. The principle of CNC high gloss machining is to use special special tools on precision CNC machining equipment to achieve shiny machining surface effect with scientific and reasonable cutting parameters and processes.
In recent years, with the development of high-performance and high-precision CNC machine tools and the emergence of high-performance metal cutting tools, CNC high finish machining has made a great breakthrough. It is possible to replace grinding with milling (turning), which has become the goal pursued by the machining industry. The principle of CNC high gloss machining is to use special special tools on precision CNC machining equipment to achieve shiny machining surface effect with scientific and reasonable cutting parameters and processes.
Machine Tool
The use of precision CNC machine tools is the prerequisite for high gloss machining. The machine tool should have good rigidity and precision, such as precision CNC engraving machine (general speed: 20000 rpm).
Tool
The use of diamond tools has contributed to the high gloss effect. Diamond cutter is the standard configuration of CNC high gloss machining industry.
The edge of a good diamond tool can not see any rough edge of the notch under a high-power microscope. The cutting edge can withstand long-term cutting without change. The friction coefficient between diamond and non-ferrous metals is very small, so the chip is not easy to stick to the blade, and there is no chip buildup. Therefore, the blade is always kept to directly cut the workpiece during the processing, and the brightness can be guaranteed.
The edge of the high gloss milling tool is wide, and the small rake angle or negative rake angle and the edge inclination angle close to zero are used. When the high gloss milling process is performed, the tool performs high-speed cutting on the one hand, and on the other hand, because the rake angle of the tool is very small, the tool edge has a scraping and extrusion effect on the machined surface, which makes the workpiece surface obtain a very high finish and produce a hardening layer, The surface hardness and wear resistance of the workpiece are improved.
In addition to the geometric shape of the workpiece, the geometric shape of the tool mainly depends on the physical characteristics of the workpiece material. When processing plastic materials such as copper, aluminum and nickel, the front angle of the tool is 0 º, and the back angle is generally between 5 º and 10 º. The radius of the tool tip arc is usually 0.5~5mm. For high machine tool stiffness, a larger radius can be used to reduce the surface roughness of the workpiece. If a smaller tool tip radius is used, the feed rate must be reduced accordingly to avoid deterioration of the surface roughness. When machining porous materials such as silicon, germanium, CaF2 and ZnS, the rake angle of the tool is generally – 15 º~- 45 º. The optimum front angle depends not only on the material itself, but also on the rigidity of the machine tool and clamping system, which is best determined through production tests.
Disc milling cutter shall be selected for high finish milling. The cutter head diameter shall be larger according to the size of the plane to be milled, with better rigidity and good positioning accuracy. The size of the cutter head will change the grain and effect of the milled plane. The number of blades can be single or multiple. However, it is difficult and time-consuming to adjust the consistency of each blade with multiple blades. Single tool milling is better.
Diamond tools look expensive and require a large investment at a time, but natural diamonds are extremely hard and wear-resistant. According to statistics, the life of diamond turning tools is 25 times that of high-speed steel turning tools, and each diamond tool can be reground 6~15 times. Therefore, the tool consumption of each part is negligible, and stable size and high brightness can be obtained.
Workpiece
Materials suitable for high gloss processing include aluminum, copper, stainless steel, etc. When processing aluminum, its brightness is the brightest, and the tool wear is the smallest; When machining copper, its brightness is relatively light, and the tool wear is next. When processing stainless steel, its brightness is gray matt, and the tool wear is also large.
The cutting speed of mirror milling is usually about 30m/s. In order to process a perfect workpiece, the spindle must be dynamically balanced after tool change to minimize the ripple on the workpiece surface caused by dynamic imbalance.
Diamond tools have good thermal conductivity and small cutting amount, so it is unnecessary to add coolant. On the contrary, the addition of coolant not only increases the trouble of cleaning after machining, but also the coolant mixed with iron filings often becomes the cause of blade breakage.
The defect of highlight is that the contour of the product is required to be high and stable, otherwise the highlight will be uneven (big and small edges, etc.).
In order to obtain safety technical data containing all relevant information (such as tools, materials, processing technology, etc.) and make it an optimal combination, it often requires an experience exploration and running in process.
Application
In Guangdong, the trend of hardware highlight processing is obvious. Aluminum highlights are most widely used in digital product shells, and can be oxidized for the second time after highlights to enhance the wear resistance of highlights. Stainless steel highlights have also been used in some high-end digital cameras and mobile phones.